Soil: The Roots of Sustainable Agriculture
John Ikerd
Professor Emeritus, University of Missouri
http://www.ssu.missouri.edu/faculty/jikerd/papers/SFTsoils.htm
All life is rooted in the soil. All living things, including humans, need food of one kind or another. Life also depends on air and water, but nothing can live with air and water alone. Living things not directly rooted in the soil – things that live in the sea, on rocks, or on trees, for example – still require minerals that come from the earth. They must have “soil” from somewhere. Living things other than plants get their food from plants or from other living things that feed on plants, and plants feed on the soil. By one means of another, all life is rooted in the soil. The purpose of a sustainable agriculture is to sustain human life, and thus, sustainable farming must be rooted in the soil.
I am an economist, not a soil scientist. So, when I talk about the soil, I try to stick to the things that almost anyone might already know or at least can understand. As I was doing some reading on the subject of soil, I ran across a delightful little book, “The Great World’s Farm,” written by an English author, Selina Gaye, somewhere around the turn of the 20th century. Back then people didn’t know so much about everything, so they could get more of what they knew about a lot of different things into a little book. The book begins by explaining how soil is formed from rock, proceeds through growth and reproduction of plants and animals, and concludes with cycles of life and the balance of nature. The book stresses throughout that all life is rooted in the soil.
Initially, molten lava covered all of the crust of the earth. So, all soil started out as rock. Most plants had to wait until rock was pulverized into small particles before they could feed on the minerals contained in the rock. Chemical reaction with oxygen and carbon dioxide, wearing away by wind and water, expansion and contraction from heating and cooling, and rock slides and glaciers have all played important roles in transforming the earth’s crust from rock into soil. However, living things also help create soil for other living things.
Lichens are a unique sort of plant that can grow directly on rock. Their spores settle on rock and begin to grow. They extract their food by secreting acids, which dissolve the minerals contained in the rock. As lichens grow and die, minerals are left in their remains to provide food for other types of plants. Some plants feeding on dead lichens grow roots capable of penetrating crevices in rocks caused by weathering. Growing roots can split and crumble rock further, exposing more surfaces to weathering and accelerating the process of “soil making.”
Specific types of rock contain limited varieties of minerals and will feed limited varieties of plants – even when pulverized into dust. Many plants require more complex combinations of minerals than are available from any single type of rock. So the soils made from various types of rocks had to be mixed before they would support the variety and complexity of plant life that we have come to associate with nature. Sand and dust can be carried from one place to another by wind and water, mixing with sand and dust from other rocks along the way. Glaciers have also been important in mixing soil. Some of the richest soils in the world are fertile bottomlands along flooding streams and rivers, loess hills that were blown and dropped by the wind, and soil deposits left behind by retreating glaciers.
Quoting from “The Great World’s Farm,” “No soil is really fertile, whatever the mineral matter composing it, unless it also contains some
amount of organic matter – matter derived from organized, living things, whether animal or vegetable. Organic matter alone is not enough to make a fertile soil; with less than one-half percent of organic matter, no soil can be cultivated to much purpose.” After the mixed soil minerals were bound in place by plants, and successions of plants and animals added organic matter and tilth, the mixtures became what we generally refer to as soil.
The first stages of soil formation are distinguished from the latter stages by at least one important characteristic. The initial dissolving, grinding, and mixing required millions of years, whereas, soil binding and adding organic matter can be accomplished in a matter of decades. Thus, the mineral fraction of soil is a “non-renewable” resource – it cannot be recreated or renewed within any realistic future timeframe. Whereas, the organic fraction is a renewable or regenerative resource that can be recreated or renewed over decades or at least over a few generations. Misuse can displace, degrade, or destroy the productivity of both fractions of soils within a matter of years. And, once the mineral fraction of soil is lost, its productivity is lost forever.
If there are to be productive soils in the future, we must conserve and
make wise use of the soils we have today. The soil that washes down our rivers to the sea is no more renewable than are the fossil fuels that we are mining from ancient deposits within the earth. In spite of our best efforts, some quantity of soil will be lost – at least lost to our use. Thus, our only hope for sustaining soil productivity is to conserve as much soil as we can and to build up soil organic matter and enhance the productivity of the soil that remains.
In times not too long past, the connection between soil and human life was clear and ever present. Little more than a century ago, most people were farmers and those who were not lived close enough to a farm to know that the food that gave them life came from the soil. They knew that if the soil was rich, if the rains came and the temperature was hospitable to plants and animals, food would be bountiful, and there would be plenty to eat. They knew that when droughts came, plants dried out then died, the soil was left bare, and there was little to eat. They knew when the floods came, plants were covered with water and died, the soil was left bare, and there was little to eat. They knew very well that their physical well-being, if not their lives, depended on the things that came from the soil.
Today, the connection between soil and life is no less critical but is no longer so direct or so clear. Most urban dwellers also have lost all sense of personal connection to the farm or the soil. During most of the past century many people living in cities either had lived on a farm at one time or knew someone, usually a close relative, who still lived on a farm. Their connection with farming gave them some understanding of their connectedness with the soil. At least they knew that “land” meant something more than just a place to play or space to be filled with some form of “development.” But these personal connections have been lost with the aging of urbanization. One of the most common laments among farmers today is that “people no longer know where their food comes from.” For most, any real understanding of the direct connection between soil and life has been lost. It’s sad but true.
Still, all of life depends upon soil. All life requires food and there is simply no other source of food except living things that depend directly or indirectly on the soil. Farmers are the living beings who care for the land, plant the seeds, and nurture the life that springs from the soil. This foundational principle of natural science, of human health, and of social studies should be taught at every level in every school in the world -- beginning in kindergarten and continuing through college. The connection between healthy soils and human health and life is as fundamental as our connection with the air we breathe, the water we drink, and the food we eat. It’s just less obvious.
Quite possibly, no aspect of education is more critical to the sustainability of human life on earth than is a broad understanding of the critical linkage between the health and life of soil and the health and life of humans. A sustainable agriculture is but the means by which life is brought from the soil and by which the health of the soil is sustained to support future human life. Even the economic and social dimensions of sustainability may be best understood in terms of ecological principles connecting people with the earth in a web of life. Many students may not be particularly interested in farming, but everyone can relate to food and everyone experiences the earth.
Recently, I was asked to participate in a discussion of future directions for soils programs of the University of Missouri. Some of us suggested that future research and education programs should focus on creating a better understanding, among students and the public alike, of the critical linkages among soil health, human health, and societal health. As scientists have focused ever more narrowly within their respective disciplines, we have degraded the natural productivity of our soils, have destroyed the ability of farms to support rural economies, and have diminished the sustainability of human society. If were are to build a sustainable society, scientists of all disciplines eventually must address the full ecological, economic, and social implications of their work. But, the science of sustainability must begin with sustaining the life of our soils – where roots of a sustainable agriculture must grow. |
